IR-192 VERSUS CO-60 BOOST IN 3-7-CM BREAST-CANCER TREATED BY IRRADIATION ALONE - FINAL RESULTS OF A RANDOMIZED TRIAL

This prospective randomized trial compared an iridium-192 implant boos t with a cobalt-60 external irradiation boost to the primary tumor sit e, in 255 patients with breast cancers 3-7 cm in diameter. All patient s had a partial (>50%) or complete response following primary external beam irradiation of 58 Gy to the whole breast, as well as irradiation to the axillary, supraclavicular and internal mammary nodes. Patients with clinically positive axillary nodes also received a cobalt-60 10- 15 Gy boost to the inferior axilla. All patients had core biopsy only. Both groups were comparable in age, tumor size, node involvement, gra de, and progesterone receptor levels. The boost dose was 20 Gy in both groups. At the median 8-year follow-up, the breast recurrence risk wa s 24% in the iridium group and 39% in the cobalt group (p = 0.02). Whe n adjusted to other prognostic and treatment factors, the brachytherap y boost decreased the breast recurrence risk by 60%. The 8-year breast preservation rates were 81% and 67%, respectively (p = 0.024). Cosmet ic outcome in both groups was evaluated in 120 patients with a minimum 3-year follow-up and was comparable in both groups. This study demons trates that in selected patients with large tumors treated with irradi ation alone, local control and breast preservation rates are improved by the use of brachytherapy to boost the primary tumor.